1. Field of the Invention
The invention relates to a control apparatus of a transmission. More particularly, the invention relates to technology for canceling an upshift in a transmission.
2. Description of the Related Art
A transmission that shifts automatically is known. The speed ratios of the transmission are set taking factors such as fuel efficiency and acceleration required by the driver into account. For example, FIG. 7 of Japanese Patent Application Publication No. 7-35228 (JP-A-7-35228) illustrates a shift according to a shift map that has the throttle opening amount (or the accelerator operation amount) and the vehicle speed as parameters.
FIG. 7 of JP-A-7-35228 shows only downshift lines that establish a downshift condition, but in a typical shift map, upshift lines that establish an upshift condition is set in addition to the downshift lines so that there is hysteresis between the downshift lines.
However, in a transmission that shifts according to a shift map, if the accelerator operation amount or the throttle opening amount increases right after an upshift condition has been satisfied, it is possible that that upshift condition may cease to be satisfied before an upshift is completed.
In this case, the upshift may continue to be performed even though the driver requires acceleration. As a result, the driving force necessary to achieve the acceleration required by the driver may no longer be able to be obtained.